I have a set of Staun's. I really like them. They have three different pressure ranges, I have the 6-30psi ones. I think I paid $57 for them. Once I get my bead locks on, I may get a 1-10psi set.
I usually just screw them on when I get to the point of knowing I want to air the tires down, it takes a few minutes for them to deflate. But they shut off when the air down pressure is reached.
It did take some time adjusting them the first time, I used a spare tire, and kept adjusting reach one until I had them set. Once this was done I have not had to readjust them.